In the industrial coating of substrates, especially metal substrates, such as autobodies, vessels, etc., the coating systems are typically passed into the coating apparatus from stock tanks through systems of lines. If, for example, 2-component systems comprising coating material and curing agent are employed, these are led from separate stock tanks by way of so-called ring lines from which the components can be taken off at any desired point. In order to obtain uniform coating results it is necessary for the coating components to be applied to the substrate in defined amounts. Precise metering of the coating material, which is constant over the entire course of the procedure, can generally only be obtained if the consistency of the coating material as well, i.e. its viscosity and the homogeneous distribution of the individual coating components in the formulation, remains constant and any fluctuations in viscosity are minor.
In the course of transportation through the ring lines, the coating materials are exposed to high shear stress, which can in some cases result in changes in their viscosity, these changes then leading to a deterioration in the coating outcome.